1. Field of the Invention
The present invention relates to a digital signal processing circuit which is used in the field of the digital audio apparatus and the like.
2. Prior Art
Conventionally, there is a well-known DSP (Digital Signal Processing Circuit), which stores the digital signal to be transmitted in one word by every predetermined period, and then carries out the convolution computation on the digital signal to be stored during the predetermined time. This type of DSP is used for various signal processings such as filtering process, reverberation imparting process and the like. In many of the DSPs which carry out the fixed digital signal processing or small-scale convolution computation, by storing coefficients used for the convolution computation in ROM in advance, the stored coefficients are sequentially read out from ROM and convolution computation is carried out based on the rear coefficients.
In the DSP for use in the audio field which imparts the reverberation effect to the musical tone, the coefficients used for the convolution computation must be changed in response to the condition of acoustical space. Similarly, a plenty of other applications of DSP require the change of the coefficients for use in the convolution computation. As the DSP which satisfies such requirement, there is a DSP which provides RAM as means for storing the coefficients used for the convolution computation. According to this type of DSP, by changing coefficients stored in RAM, various signal processing can be performed. In this case, however, there is a problem in that the writing address is required to be designated by each coefficient, thus, the operation for setting the coefficients is troublesome. Additionally, in order to implement the large-scale convolution computation, the DSP can be embodied by use of plural LSIs. In this case, a series of the coefficients used for the convolution computation must be allocated into corresponding LSIs. However, it requires the external control circuit to be provided for the DSP in order to control the operation for writing the coefficients by each of the allocated coefficients.